Why is a chilli hot and other chilli facts

Carolina Reaper (HP22B) © Copyright 2014 Chilli of the Valley

By Dan Reed, science made simple’s chili expert, or “Chilliologist”. 

How hot is hot? What makes a chilli hot?

What’s the hottest chilli you can get?

On the 25th November 2014, Matt Simpson, of Simpsons Seeds and plants, based in Wiltshire, broke the record for growing the UK’s hottest chilli. The chilli, known as Katie, measured a whopping 1,590,000 Scoville heat units (SHU), some 200,000 units hotter than the UK’s previous record holder, the Naga Viper. The current Guninness World Record holder is known as the HP22B, or more commonly, the Carolina Reaper, measuring up to an incredible 2.2 million Scoville units.

“Don’t Take the Pith!” Where is the heat in a chilli?


Contrary to popular belief, seeds are not the hottest part of the chilli, it is in fact the membrane to which they are attached (the white bit), but when the seeds are removed, the membrane is often scraped out with the seeds. For more information, keep an eye out for our Chilli busking sessions at festivals throughout 2015.

What is a Scoville, what makes chillies hot?  And why should I care?!

The Scoville Heat Unit is the heat measurement of a chilli. It is named after Wilbur Scoville, an American Pharmacist, who in 1912 devised the “Scoville Organoleptic Test” to measure the spicy heat, or piquancy, of chilli peppers. The measurement is taken by extracting some of the capsaicin from a chilli, and then gradually diluting it into a sugar and water mix, until the heat is barely detectable by a panel of tasters. The degree of dilution gives the chilli its place in the scale. A bell pepper has a zero Scoville rating, whilst a habanero has 100,000 – 350,000 Scoville rating, meaning it must be diluted this many times before its Capsaicin levels become undetectable.

More recently, a more modern way of measuring chilli heat is through High Performance Liquid Chromatography (HPLC). Results tend to be 20 – 40% lower than Scoville rating. More humane, but less fun!

To give the Carolina Reapers 2.2 million SHU a little more meaning, a bottle of Tabasco sauce rates between 2,500 and 5,000 and pepper spray averages in at around the 2 million mark!


chilli of the valley chillies

A colourful range of chillies © Copyright 2014 Chilli of the Valley

So what is it exactly that makes a chilli hot?

Capsaicin is the chemical compound found in chillies, which makes them hot.Pure capsaicin measures 16,000,000 scoville units.

This is the Everest of the heat scale – nothing is hotter. It is an irritant to mammals, but not effective against birds, snails or slugs, which may explain why they enjoy munching your chillies. Capsaicin will take effect upon sensitive skin, eye contact, and inhalation, and cause burning/stinging pain, and can also produce nausea, vomiting, abdominal pain… and burning diarrhoea. Nice! It does not actually cause a chemical burn, but reacts with sensory neurons which stimulate the brain into believing the exposed area is experiencing excessive heat or abrasive damage.

Capsaicin is hydrophobic – it doesn’t dissolve in water. This means that drinking water if you eat a hot chilli will not help. It is however, soluble in both oil and alcohol, drinking and/or eating dairy products (milk, yogurt, cheese, etc) will help, as will drinking spirits… but beer or cider won’t do much to help.

With time, you can train your body to tolerate the burning sensations of eating chillies, and find that you can work your way up the chilli hierarchy. If you were to eat a Jalapeno every day for a month, what may seem hot at the start, would definitely become tolerable by the end. The one problem then is that you’re likely to find yourself looking for hotter chillies (or hot sauces) to eat, to quench the desire for hot food – Eating hot chillies can be an addictive thing, just ask any chilli head why they enjoy eating them so much.

Five of the hottest. From left to right – Carolina Reaper (HP22B), Trinidad Moruga Scorpion, Trinidad Douglah, Trinidad Scorpion, Bhut Jolokia. © Copyright 2014 Chilli of the Valley

According to a newspaper article in the Independent newspaper on 22nd June 2012, “in 2010, sales of hot sauces went up by 20 per cent. Today’s British diners are eating food 400 times hotter than our grandparents could handle. And we eat more of it than anyone else in Europe” (www.independent.co.uk/life-style/food-and-drink/features/some-like-it-hot-how-britain-got-the-taste-for-spice-7873518.html) With over 3,000 (and growing) varieties of chilli available accross the globe, varying in size, shape, colour, heat, and flavour, these versatile little nuggets of heat will feature quite prominently in the UK menus for the foreseeable future.

Where can I get some?

If you fancy trying some chilli sauces made by me, using chillies I have lovingly grown here in Wales then check out the Chilli of the Valley website. And don’t forget to enter code: smsncd for your 10% discount!

All of the chillies featured in this blog were home grown in Wales for Chilli of the Valley , proving that you don’t need the sunny tropics of the Caribbean or blistering heat of South America to grow a chilli pepper, just a greenhouse, polytunnel, or even a sunny windowsill, and a little love.


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